bubble.p

{$C3000}
program bubble(input, output);
{ Program   : bubble
  Input     : 1) Number of data items (maximum 500)
	      2) The data items  Operation : Sorts the data using a bubble sort, the number of comparisons
	      and data accesses being counted.
  Output    : The number of comparisons and accesses and the sorted data	      in ascending order.  Bugs      : 1) The program does not check for invalid data type on input
	      so entering an invalid integer will cause a fatal crash.
}

const  maxitems = 500;
type  datatype = array [1..maxitems] of integer;
var
  nocomparisons, noaccesses, size: integer;
  data: datatype;

{ =================================================================================================================== }
{ Function   : readsizedata
  Input      : From file (input) ie the terminal keyboard, the number               of data items to be read in ( an integer)
  Operation  : Repeats the question until a valid number is entered
  Output     : The number of data items
}

function readsizedata: integer;
  var
    tempsize: integer;
  begin
    writeln('Please enter the number of data items');
    read(tempsize);
    while (tempsize < 2) or (tempsize > maxitems) do begin
      writeln('Please enter a number greater than 1 and less than ', maxitems+1: 3);
      read(tempsize)
    end; { while }
    readsizedata := tempsize
  end; { readsizedata }

{ ==================================================================================================================== }

{ Procedure : inputdata
  Input     : Number of items to accept
  Operation : Reads the data items from the input file and without		checking for validity, stores them in the data array.
  Output    : A data array containing integers
}

  procedure inputdata(var data: datatype; size: integer);
  var
    counter: integer;
  begin
    writeln;
    for counter := 1 to size do begin
      write('Please enter item (', counter: 3, ') :');
      read(data[counter])
    end
  end; { inputdata }

{ =================================================================================================================== }

{ Procedure : sortdata
  Input     : The number of data items and the items themselves
  Operation : Sorts the data using a bubble sort into ascending order
	      and counts the number of array accesses and the number of
	      comparisons.
  Output    : The sorted data , the number of comparisons and the number
	      of array accesses
}

  procedure sortdata(var data: datatype;
    size: integer;
    var n comparisons: integer;
    var noaccesses: integer);
  var
    limit, counter, tempdatum: integer;
    finished: boolean;
  begin
    nocomparisons := 0;
    noaccesses := 0;
    limit := size;
    repeat
      finished := TRUE;
      for counter := 1 to limit - 1 do begin
	nocomparisons := nocomparisons + 1;
	noaccesses := noaccesses + 2;
	if data[counter] > data[counter + 1] then begin
	  noaccesses := noaccesses + 4;
	  tempdatum := data[counter];
	  data[counter] := data[counter + 1];
	  data[counter + 1] := tempdatum;
	  finished := FALSE
	end
      end;
      limit := limit - 1
    until (limit = 2) or finished
  end; { sortdata }

{ ==================================================================================================================== }

{ Procedure : printdata
  Input     : The data array, its size, the number of comparisons and accesses
  Operation : Prints the header information and the data items in order
  and Output
}
  procedure printdata(data: datatype; size, nocomparisons, noaccesses: integer);
  var
    counter: integer;
  begin
    writeln;
    writeln('There were ', nocomparisons: 5, ' comparisons');
    writeln('       and ', noaccesses: 5, ' accesses');
    writeln;
    for counter := 1 to size do
       writeln('Item (', counter: 3, ') ', data[counter]: 10);
    writeln;
  end; { printdata }

{ ==================================================================================================================== }

{ Function  : userisfinished
  Input     : Single character 'y' or 'n' followed by return
  Operation : Checks if input is valid and repeats until it is so
  Output    : TRUE or FALSE depending on the input
}

function userisfinished : boolean;
var
  answer : char;
begin
  readln;
  { To clear the end of line character }
  write('Do you want to enter more sets of data?');
  repeat
    readln(answer);
    if not(answer in ['y','n']) then
      begin
	writeln;
	write('Please type either y or n, more data? ');
      end;
  until (answer in ['y','n']);
  userisfinished := (answer='n')
end; { userisfinished }

{ =================================================================================================================== }

begin { main program }
  repeat
    writeln;
    size := readsizedata;
    inputdata(data, size);
    sortdata(data, size, nocomparisons, noaccesses;
    printdata(data, size, nocomparisons, noaccesses)
  until userisfinished
end.